1. Chapter 35 – Health Physics
RTMR 284 – Winter 2013

2. Health Physics
The term health physics was coined during the early days of the Manhattan Project (development of the atomic bomb).
Health Physics is concerned with providing occupational radiation protection and minimizing radiation dose to public.
National Academy of Sciences identified the 20 greatest scientific and technical accomplishments of the 20th century: Medical Imaging was 14th !
Radiation is more than dangerous, deadly, or harmful, but used it small doses able to diagnose problems early and help fight cancers with therapy.

3. Cardinal Principles of Rad Protection
TIME
DISTANCE
SHIELDING

4. ALARA As Low As Reasonably Achievable
Exposure Time = Exposure rate (Gya/hr) * Exposure time (min)
!!! remember to keep units the same -># min / 60 (min/hr)
Distance….The more you have the less exposure you will receive
Inverse Square Law! Int 1/Int 2 = (Dist 2)2 / (Dist 1)2
Shielding…..The amount of a protective barrier reduces radiation intensity can be estimated with the HVL (half value layer) or the TVL (tenth value layer) 1TVL=3.3HVL

5. Effective Dose / Whole Body Equivalent Dose
The Equivalent whole-body dose!
When only part of the body is exposed during radiography the risk of a stochastic radiation response is not proportional to the tissue does, but rather the effective dose (E).
Effective dose is the weighted average dose to each of the tissues:
Effective dose =
tissue dose * Weighting factor
E= € Di * W t
We assume occupational effective dose = 10% of the monitor dose

7. Radiologic Terrorism All Rescue and Medical emergencies should
be attended to before radiologic concerns are addressed
Being exposed to radiation does not make a person radioactive!
Devices used for terrorism:
RED – Radiation Exposure Device (sealed)
RDD- Radiologic Dispersal Device (bomb)
IND- Improvised Nuclear Device (nuc explosion / weapons)
Establishment of boundaries are used to contain exposure
In the hospital setting a Radiation Safety Officer is in charge
of a response plan in case of a high radiation reading
Detection Equipment are used to provide early warnings